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          LV05-07-Linux系统-01-系统信息获取
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              <table>    <tr>        <td align="center" width=150px>Windows</td>        <td align="left">windows11</td>    </tr>    <tr>        <td align="center">Ubuntu</td>        <td align="left">Ubuntu16.04的64位版本</td>      </tr>    <tr>        <td align="center">VMware® Workstation 16 Pro</td>        <td align="left">16.2.3 build-19376536</td>      </tr>    <tr>        <td align="center">SecureCRT</td>        <td align="left">Version 8.7.2 (x64 build 2214)   -   正式版-2020年5月14日</td>      </tr>    <tr>        <td align="center">开发板</td>        <td align="left">正点原子 i.MX6ULL Linux阿尔法开发板</td>      </tr>    <tr>        <td align="center">uboot</td>        <td align="left">NXP官方提供的uboot，NXP提供的版本为uboot-imx-rel_imx_4.1.15_2.1.0_ga(使用的uboot版本为U-Boot 2016.03)</td>      </tr>    <tr>        <td align="center">linux内核</td>        <td align="left">linux-4.15(NXP官方提供)</td>      </tr>    <tr>        <td align="center">STM32开发板</td>        <td align="left">正点原子战舰V3(STM32F103ZET6)</td>      </tr></table>
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<h1 id="一、系统信息"><a href="#一、系统信息" class="headerlink" title="一、系统信息"></a><font size=3>一、系统信息</font></h1><h2 id="1-uname-函数"><a href="#1-uname-函数" class="headerlink" title="1. uname() 函数"></a><font size=3>1. uname() 函数</font></h2><h3 id="1-1-函数说明"><a href="#1-1-函数说明" class="headerlink" title="1.1 函数说明"></a><font size=3>1.1 函数说明</font></h3><p>在<code>linux</code>下可以使用<code>man 2 uname</code>命令查看该函数的帮助手册。</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/utsname.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 函数声明 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">uname</span><span class="params">(<span class="keyword">struct</span> utsname *buf)</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数是一个系统调用，可以用于获取系统的一些信息。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li><code>buf</code>：<code>struct utsname</code>类型结构体指针变量，指向一个存储系统信息的<code>struct utsname</code>结构体类型对象，该结构体类型的成员都是<code>char</code>类型的字符串。</li>
</ul>
<details class="folding-tag" blue><summary> 点击查看 struct utsname 结构体说明 </summary>
              <div class='content'>
              <p>在使用<code>man</code>查看帮助手册的时候，有该结构体的原型：</p><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">struct</span> <span class="title">utsname</span></span></span><br><span class="line"><span class="class">&#123;</span></span><br><span class="line">	<span class="type">char</span> sysname[];    <span class="comment">/* Operating system name (e.g., &quot;Linux&quot;) */</span></span><br><span class="line">	<span class="type">char</span> nodename[];   <span class="comment">/* Name within &quot;some implementation-defined network&quot; */</span></span><br><span class="line">	<span class="type">char</span> release[];    <span class="comment">/* Operating system release (e.g., &quot;2.6.28&quot;) */</span></span><br><span class="line">	<span class="type">char</span> version[];    <span class="comment">/* Operating system version */</span></span><br><span class="line">	<span class="type">char</span> machine[];    <span class="comment">/* Hardware identifier */</span></span><br><span class="line"><span class="meta">#<span class="keyword">ifdef</span> _GNU_SOURCE</span></span><br><span class="line">	<span class="type">char</span> domainname[]; <span class="comment">/* NIS or YP domain name */</span></span><br><span class="line"><span class="meta">#<span class="keyword">endif</span></span></span><br><span class="line">&#125;;</span><br></pre></td></tr></table></figure><p>成员说明如下：</p><table>    <tr><td align="center" width=150px>sysname</td><td align="left">当前操作系统的名称</td></tr>    <tr><td align="center" width=150px>nodename</td><td align="left">网络上的名称（主机名）</td></tr>    <tr><td align="center" width=150px>release</td><td align="left">操作系统内核版本</td></tr>    <tr><td align="center" width=150px>version</td><td align="left">操作系统发行版本</td></tr>    <tr><td align="center" width=150px>machine</td><td align="left">硬件架构类型</td></tr>    <tr><td align="center" width=150px>domainname</td><td align="left">当前域名</td></tr></table>
              </div>
            </details>

<p><strong>【返回值】</strong><code>int</code>类型，成功返回<code>0</code>，失败返回<code>-1</code>，并设置<code>errno</code>。</p>
<p><strong>【使用格式】</strong>一般情况下基本使用格式如下：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需要包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/utsname.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 至少应该有的语句 */</span></span><br><span class="line"><span class="class"><span class="keyword">struct</span> <span class="title">utsname</span> <span class="title">os_info</span>;</span></span><br><span class="line">uname(&amp;os_info);</span><br></pre></td></tr></table></figure>

<p><strong>【注意事项】</strong><code>none</code></p>
<h3 id="1-2-使用实例"><a href="#1-2-使用实例" class="headerlink" title="1.2 使用实例"></a><font size=3>1.2 使用实例</font></h3><details class="folding-tag" blue><summary> 点击查看实例 </summary>
              <div class='content'>
              <figure class="highlight c"><figcaption><span>test.c</span></figcaption><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/utsname.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> arc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">utsname</span> <span class="title">os_info</span>;</span></span><br><span class="line">	<span class="type">int</span> ret; <span class="comment">/* 获取信息 */</span></span><br><span class="line">	ret = uname(&amp;os_info);</span><br><span class="line">	<span class="keyword">if</span> (ret == <span class="number">-1</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror(<span class="string">&quot;uname error&quot;</span>);</span><br><span class="line">		<span class="keyword">return</span> <span class="number">-1</span>;</span><br><span class="line">	&#125;</span><br><span class="line"></span><br><span class="line">	<span class="comment">/* 打印信息 */</span></span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;操作系统名称: %s\n&quot;</span>, os_info.sysname);</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;主机名: %s\n&quot;</span>, os_info.nodename);</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;内核版本: %s\n&quot;</span>, os_info.release);</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;发行版本: %s\n&quot;</span>, os_info.version);</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;硬件架构: %s\n&quot;</span>, os_info.machine);</span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure><p>在终端执行以下命令编译程序：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">gcc test.c -Wall # 生成可执行文件 a.out </span><br><span class="line">./a.out # 执行可执行程序</span><br></pre></td></tr></table></figure><p>然后，终端会有以下信息显示：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">操作系统名称: Linux</span><br><span class="line">主机名: vm</span><br><span class="line">内核版本: 5.11.0-49-generic</span><br><span class="line">发行版本: #55-Ubuntu SMP Wed Jan 12 17:36:34 UTC 2022</span><br><span class="line">硬件架构: x86_64</span><br></pre></td></tr></table></figure>
              </div>
            </details>

<h2 id="2-sysinfo-函数"><a href="#2-sysinfo-函数" class="headerlink" title="2. sysinfo() 函数"></a><font size=3>2. sysinfo() 函数</font></h2><h3 id="2-1-函数说明"><a href="#2-1-函数说明" class="headerlink" title="2.1 函数说明"></a><font size=3>2.1 函数说明</font></h3><p>在<code>linux</code>下可以使用<code>man 2 sysinfo</code>命令查看该函数的帮助手册。</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/sysinfo.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 函数声明 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">sysinfo</span><span class="params">(<span class="keyword">struct</span> sysinfo *info)</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数是一个系统调用，可以用于获取系统的一些相关信息。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li><code>info</code>：<code>struct sysinfo</code>类型结构体指针变量，指向一个存储系统相关信息的<code>struct sysinfo</code>结构体类型对象。</li>
</ul>
<details class="folding-tag" blue><summary> 点击查看 struct sysinfo结构体说明 </summary>
              <div class='content'>
              <p>在使用<code>man</code>查看帮助手册的时候，有该结构体的原型：</p><div class="tabs" id="tabname1"><ul class="nav-tabs"><li class="tab active"><a href="#tabname1-1">未翻译</a></li><li class="tab"><a href="#tabname1-2">已翻译</a></li></ul><div class="tab-content"><div class="tab-pane active" id="tabname1-1"><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">struct</span> <span class="title">sysinfo</span></span></span><br><span class="line"><span class="class">&#123;</span></span><br><span class="line">	<span class="type">long</span> uptime;             <span class="comment">/* Seconds since boot */</span></span><br><span class="line">	<span class="type">unsigned</span> <span class="type">long</span> loads[<span class="number">3</span>];  <span class="comment">/* 1, 5, and 15 minute load averages */</span></span><br><span class="line">	<span class="type">unsigned</span> <span class="type">long</span> totalram;  <span class="comment">/* Total usable main memory size */</span></span><br><span class="line">	<span class="type">unsigned</span> <span class="type">long</span> freeram;   <span class="comment">/* Available memory size */</span></span><br><span class="line">	<span class="type">unsigned</span> <span class="type">long</span> sharedram; <span class="comment">/* Amount of shared memory */</span></span><br><span class="line">	<span class="type">unsigned</span> <span class="type">long</span> bufferram; <span class="comment">/* Memory used by buffers */</span></span><br><span class="line">	<span class="type">unsigned</span> <span class="type">long</span> totalswap; <span class="comment">/* Total swap space size */</span></span><br><span class="line">	<span class="type">unsigned</span> <span class="type">long</span> freeswap;  <span class="comment">/* Swap space still available */</span></span><br><span class="line">	<span class="type">unsigned</span> <span class="type">short</span> procs;    <span class="comment">/* Number of current processes */</span></span><br><span class="line">	<span class="type">unsigned</span> <span class="type">long</span> totalhigh; <span class="comment">/* Total high memory size */</span></span><br><span class="line">	<span class="type">unsigned</span> <span class="type">long</span> freehigh;  <span class="comment">/* Available high memory size */</span></span><br><span class="line">	<span class="type">unsigned</span> <span class="type">int</span> mem_unit;   <span class="comment">/* Memory unit size in bytes */</span></span><br><span class="line">	<span class="type">char</span> _f[<span class="number">20</span><span class="number">-2</span>*<span class="keyword">sizeof</span>(<span class="type">long</span>)-<span class="keyword">sizeof</span>(<span class="type">int</span>)]; <span class="comment">/* Padding to 64 bytes */</span></span><br><span class="line">&#125;;</span><br></pre></td></tr></table></figure></div><div class="tab-pane" id="tabname1-2"><figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">struct</span> <span class="title">sysinfo</span></span></span><br><span class="line"><span class="class">&#123;</span></span><br><span class="line">	<span class="type">long</span> uptime;             <span class="comment">/* 启动到现在经过的时间 */</span></span><br><span class="line">	<span class="type">unsigned</span> <span class="type">long</span> loads[<span class="number">3</span>];  <span class="comment">/* 1, 5, and 15 minute load averages */</span></span><br><span class="line">	<span class="type">unsigned</span> <span class="type">long</span> totalram;  <span class="comment">/* 总的可用的内存大小 */</span></span><br><span class="line">	<span class="type">unsigned</span> <span class="type">long</span> freeram;   <span class="comment">/* 还未被使用的内存大小 */</span></span><br><span class="line">	<span class="type">unsigned</span> <span class="type">long</span> sharedram; <span class="comment">/* 共享的存储器的大小 */</span></span><br><span class="line">	<span class="type">unsigned</span> <span class="type">long</span> bufferram; <span class="comment">/* 共享的存储器的大小 */</span></span><br><span class="line">	<span class="type">unsigned</span> <span class="type">long</span> totalswap; <span class="comment">/* 交换区大小 */</span></span><br><span class="line">	<span class="type">unsigned</span> <span class="type">long</span> freeswap;  <span class="comment">/* 还可用的交换区大小 */</span></span><br><span class="line">	<span class="type">unsigned</span> <span class="type">short</span> procs;    <span class="comment">/* 当前进程数目 */</span></span><br><span class="line">	<span class="type">unsigned</span> <span class="type">long</span> totalhigh; <span class="comment">/* 总的高内存大小 */</span></span><br><span class="line">	<span class="type">unsigned</span> <span class="type">long</span> freehigh;  <span class="comment">/* 可用的高内存大小 */</span></span><br><span class="line">	<span class="type">unsigned</span> <span class="type">int</span> mem_unit;   <span class="comment">/* 以字节为单位的内存大小 */</span></span><br><span class="line">	<span class="type">char</span> _f[<span class="number">20</span><span class="number">-2</span>*<span class="keyword">sizeof</span>(<span class="type">long</span>)-<span class="keyword">sizeof</span>(<span class="type">int</span>)]; <span class="comment">/* Padding to 64 bytes */</span></span><br><span class="line">&#125;;</span><br></pre></td></tr></table></figure></div></div></div>
              </div>
            </details>

<p><strong>【返回值】</strong><code>int</code>类型，成功返回<code>0</code>，失败返回<code>-1</code>，并设置<code>errno</code>。</p>
<p><strong>【使用格式】</strong>一般情况下基本使用格式如下：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需要包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/sysinfo.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 至少应该有的语句 */</span></span><br><span class="line"><span class="class"><span class="keyword">struct</span> <span class="title">sysinfo</span> <span class="title">sys_info</span>;</span></span><br><span class="line">sysinfo(&amp;sys_info);</span><br></pre></td></tr></table></figure>

<p><strong>【注意事项】</strong><code>none</code></p>
<h3 id="2-2-使用实例"><a href="#2-2-使用实例" class="headerlink" title="2.2 使用实例"></a><font size=3>2.2 使用实例</font></h3><details class="folding-tag" blue><summary> 点击查看实例 </summary>
              <div class='content'>
              <figure class="highlight c"><figcaption><span>test.c</span></figcaption><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;sys/sysinfo.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> arc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="class"><span class="keyword">struct</span> <span class="title">sysinfo</span> <span class="title">sys_info</span>;</span></span><br><span class="line">	<span class="type">int</span> ret; <span class="comment">/* 获取信息 */</span></span><br><span class="line">	ret = sysinfo(&amp;sys_info);</span><br><span class="line">	<span class="keyword">if</span> (ret == <span class="number">-1</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror(<span class="string">&quot;sysinfo error&quot;</span>);</span><br><span class="line">		<span class="keyword">return</span> <span class="number">-1</span>;</span><br><span class="line">	&#125;</span><br><span class="line"></span><br><span class="line">	<span class="comment">/* 打印信息 */</span></span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;uptime: %ld\n&quot;</span>, sys_info.uptime);</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;totalram: %lu\n&quot;</span>, sys_info.totalram);</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;freeram: %lu\n&quot;</span>, sys_info.freeram);</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;sharedram: %lu\n&quot;</span>, sys_info.sharedram);</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;bufferram: %lu\n&quot;</span>, sys_info.bufferram);</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;totalswap: %lu\n&quot;</span>, sys_info.totalswap);</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;freeswap: %lu\n&quot;</span>, sys_info.freeswap);</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;procs: %u\n&quot;</span>, sys_info.procs);</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;totalhigh: %lu\n&quot;</span>, sys_info.totalhigh);</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;freehigh: %lu\n&quot;</span>, sys_info.freehigh);</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;mem_unit: %d\n&quot;</span>, sys_info.mem_unit);</span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure><p>在终端执行以下命令编译程序：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">gcc test.c -Wall # 生成可执行文件 a.out </span><br><span class="line">./a.out # 执行可执行程序</span><br></pre></td></tr></table></figure><p>然后，终端会有以下信息显示：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line">uptime: 9035</span><br><span class="line">totalram: 4083724288</span><br><span class="line">freeram: 1898512384</span><br><span class="line">sharedram: 38412288</span><br><span class="line">bufferram: 110936064</span><br><span class="line">totalswap: 1218854912</span><br><span class="line">freeswap: 1218854912</span><br><span class="line">procs: 532</span><br><span class="line">totalhigh: 0</span><br><span class="line">freehigh: 0</span><br><span class="line">mem_unit: 1</span><br></pre></td></tr></table></figure>
              </div>
            </details>

<h2 id="3-gethostname-函数"><a href="#3-gethostname-函数" class="headerlink" title="3. gethostname() 函数"></a><font size=3>3. gethostname() 函数</font></h2><h3 id="3-1-函数说明"><a href="#3-1-函数说明" class="headerlink" title="3.1 函数说明"></a><font size=3>3.1 函数说明</font></h3><p>在<code>linux</code>下可以使用<code>man 2 gethostname</code>命令查看该函数的帮助手册。</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 函数声明 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">gethostname</span><span class="params">(<span class="type">char</span> *name, <span class="type">size_t</span> len)</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数是一个系统调用，可以用于获取<code>Linux</code>系统的主机名称，功能其实与<code>struct utsname</code>数据结构体中的<code>nodename</code>成员变量一样。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li><code>name</code>：<code>char</code>类型指针变量，指向用于存放主机名字符串的内存缓冲区。</li>
<li><code>len</code>：<code>size_t</code>类型，表示缓冲区的长度。</li>
</ul>
<p><strong>【返回值】</strong><code>int</code>类型，成功返回<code>0</code>，失败返回<code>-1</code>，并设置<code>errno</code>。</p>
<p><strong>【使用格式】</strong>一般情况下基本使用格式如下：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需要包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 至少应该有的语句 */</span></span><br><span class="line"><span class="type">char</span> hostname[<span class="number">20</span>];</span><br><span class="line">gethostname(hostname, <span class="keyword">sizeof</span>(hostname));</span><br></pre></td></tr></table></figure>

<p><strong>【注意事项】</strong><code>none</code></p>
<h3 id="3-2-使用实例"><a href="#3-2-使用实例" class="headerlink" title="3.2 使用实例"></a><font size=3>3.2 使用实例</font></h3><details class="folding-tag" blue><summary> 点击查看实例 </summary>
              <div class='content'>
              <figure class="highlight c"><figcaption><span>test.c</span></figcaption><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span> </span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;string.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> arc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="type">char</span> hostname[<span class="number">20</span>];</span><br><span class="line">	<span class="type">int</span> ret;</span><br><span class="line">	<span class="built_in">memset</span>(hostname, <span class="number">0</span>, <span class="keyword">sizeof</span>(hostname));</span><br><span class="line">	ret = gethostname(hostname, <span class="keyword">sizeof</span>(hostname));</span><br><span class="line">	<span class="keyword">if</span> (ret == <span class="number">-1</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror(<span class="string">&quot;gethostname error&quot;</span>);</span><br><span class="line">		<span class="keyword">return</span> <span class="number">-1</span>;</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;hostname=%s\n&quot;</span>, hostname);</span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure><p>在终端执行以下命令编译程序：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">gcc test.c -Wall # 生成可执行文件 a.out </span><br><span class="line">./a.out # 执行可执行程序</span><br></pre></td></tr></table></figure><p>然后，终端会有以下信息显示：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">hostname=vm</span><br></pre></td></tr></table></figure>
              </div>
            </details>

<h2 id="4-gethostname-函数"><a href="#4-gethostname-函数" class="headerlink" title="4. gethostname() 函数"></a><font size=3>4. gethostname() 函数</font></h2><h3 id="4-1-函数说明"><a href="#4-1-函数说明" class="headerlink" title="4.1 函数说明"></a><font size=3>4.1 函数说明</font></h3><p>在<code>linux</code>下可以使用<code>man 2 gethostname</code>命令查看该函数的帮助手册。</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 函数声明 */</span></span><br><span class="line"><span class="type">int</span> <span class="title function_">sethostname</span><span class="params">(<span class="type">const</span> <span class="type">char</span> *name, <span class="type">size_t</span> len)</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数是一个系统调用，可以用于设置<code>Linux</code>系统的主机名称。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li><code>name</code>：<code>char</code>类型指针变量，指向用于存放要设置的主机名字符串的内存缓冲区。</li>
<li><code>len</code>：<code>size_t</code>类型，表示缓冲区的长度。</li>
</ul>
<p><strong>【返回值】</strong><code>int</code>类型，成功返回<code>0</code>，失败返回<code>-1</code>，并设置<code>errno</code>。</p>
<p><strong>【使用格式】</strong>一般情况下基本使用格式如下：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需要包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 至少应该有的语句 */</span></span><br><span class="line"><span class="type">char</span> hostname[<span class="number">20</span>];</span><br><span class="line"><span class="built_in">strcpy</span>(hostname, <span class="string">&quot;fanhua&quot;</span>);</span><br><span class="line">sethostname(hostname, <span class="keyword">sizeof</span>(hostname));</span><br></pre></td></tr></table></figure>

<p><strong>【注意事项】</strong>必须在<code>root</code>用户运行才会生效，否则会提示没有操作权限，并且重启后主机名会恢复原来的名称。</p>
<h3 id="4-2-使用实例"><a href="#4-2-使用实例" class="headerlink" title="4.2 使用实例"></a><font size=3>4.2 使用实例</font></h3><details class="folding-tag" blue><summary> 点击查看实例 </summary>
              <div class='content'>
              <figure class="highlight c"><figcaption><span>test.c</span></figcaption><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span> </span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;string.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> arc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="type">char</span> hostname[<span class="number">20</span>];</span><br><span class="line">	<span class="type">int</span> ret;</span><br><span class="line">	<span class="built_in">memset</span>(hostname, <span class="number">0</span>, <span class="keyword">sizeof</span>(hostname));</span><br><span class="line">	ret = gethostname(hostname, <span class="keyword">sizeof</span>(hostname));</span><br><span class="line">	<span class="keyword">if</span> (ret == <span class="number">-1</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror(<span class="string">&quot;gethostname error&quot;</span>);</span><br><span class="line">		<span class="keyword">return</span> <span class="number">-1</span>;</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;hostname=%s\n&quot;</span>, hostname);</span><br><span class="line">	</span><br><span class="line">	<span class="built_in">strcpy</span>(hostname, <span class="string">&quot;fanhua&quot;</span>);</span><br><span class="line">	ret = sethostname(hostname, <span class="keyword">sizeof</span>(hostname));</span><br><span class="line">	<span class="keyword">if</span> (ret == <span class="number">-1</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror(<span class="string">&quot;sethostname error&quot;</span>);</span><br><span class="line">		<span class="keyword">return</span> <span class="number">-1</span>;</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="built_in">memset</span>(hostname, <span class="number">0</span>, <span class="keyword">sizeof</span>(hostname));</span><br><span class="line">	ret = gethostname(hostname, <span class="keyword">sizeof</span>(hostname));</span><br><span class="line">	<span class="keyword">if</span> (ret == <span class="number">-1</span>)</span><br><span class="line">	&#123;</span><br><span class="line">		perror(<span class="string">&quot;gethostname error&quot;</span>);</span><br><span class="line">		<span class="keyword">return</span> <span class="number">-1</span>;</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;hostname=%s\n&quot;</span>, hostname);</span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure><p>在终端执行以下命令编译程序：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">gcc test.c -Wall # 生成可执行文件 a.out </span><br><span class="line">./a.out # 执行可执行程序</span><br></pre></td></tr></table></figure><p>然后，终端会有以下信息显示：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">hostname=vm</span><br><span class="line">hostname=fanhua</span><br><span class="line"><span class="meta prompt_"></span></span><br><span class="line"><span class="meta prompt_"># </span><span class="language-bash">在非 root 下运行的话，会有如下信息</span></span><br><span class="line">hostname=vm</span><br><span class="line">sethostname error: Operation not permitted</span><br></pre></td></tr></table></figure>
              </div>
            </details>

<h2 id="5-sysconf-函数"><a href="#5-sysconf-函数" class="headerlink" title="5. sysconf() 函数"></a><font size=3>5. sysconf() 函数</font></h2><h3 id="5-1-函数说明"><a href="#5-1-函数说明" class="headerlink" title="5.1 函数说明"></a><font size=3>5.1 函数说明</font></h3><p>在<code>linux</code>下可以使用<code>man 3 sysconf</code>命令查看该函数的帮助手册。</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 函数声明 */</span></span><br><span class="line"><span class="type">long</span> <span class="title function_">sysconf</span><span class="params">(<span class="type">int</span> name)</span>;</span><br></pre></td></tr></table></figure>

<p><strong>【函数说明】</strong>该函数是一个库函数，可在获取系统运行时的一些配置信息。</p>
<p><strong>【函数参数】</strong></p>
<ul>
<li><code>name</code>：<code>int</code>类型，指定了要获取配置信息的编号。</li>
</ul>
<details class="folding-tag" blue><summary> 点击查看 name 可取的值 </summary>
              <div class='content'>
              <p>在使用<code>man</code>查看帮助手册的时候，会有大量的宏定义表示系统的配置信息，这里列举几个常用的：</p><table>    <tr><td align="left" width=150px>_SC_ARG_MAX</td><td align="left">exec族函数的参数的最大长度</td></tr>    <tr><td align="left" width=150px>_SC_CHILD_MAX</td><td align="left">每个用户的最大并发进程数，也就是同一个用户可以同时运行的最大进程数。</td></tr>    <tr><td align="left" width=150px>_SC_HOST_NAME_MAX </td><td align="left">主机名的最大长度。</td></tr>    <tr><td align="left" width=150px>_SC_LOGIN_NAME_MAX</td><td align="left">登录名的最大长度。</td></tr>    <tr><td align="left" width=150px>_SC_CLK_TCK</td><td align="left">每秒时钟滴答数，也就是系统节拍率。</td></tr>    <tr><td align="left" width=150px>_SC_OPEN_MAX</td><td align="left">一个进程可以打开的最大文件数。</td></tr>    <tr><td align="left" width=150px>_SC_PAGESIZE</td><td align="left">系统页大小（page size）。</td></tr>    <tr><td align="left" width=150px>_SC_TTY_NAME_MAX</td><td align="left">终端设备名称的最大长度。</td></tr></table>
              </div>
            </details>

<p><strong>【返回值】</strong><code>long</code>类型，若指定的参数<code>name</code>为无效值，则返回<code>-1</code>，并会将<code>errno</code>设置为<code>EINVAL</code>。如果<code>name</code>对应一个最大或最小限制，并且该限制是不确定的，则返回<code>-1</code>并且不更改<code>errno</code>。否则返回的值便是对应的配置值。</p>
<p><strong>【使用格式】</strong>一般情况下基本使用格式如下：</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/* 需要包含的头文件 */</span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="comment">/* 至少应该有的语句 */</span></span><br><span class="line">sysconf(_SC_TTY_NAME_MAX);</span><br></pre></td></tr></table></figure>

<p><strong>【注意事项】</strong>返回值为<code>long</code>类型，使用<code>printf</code>打印时，需要使用<code>%ld</code>。</p>
<h3 id="5-2-使用实例"><a href="#5-2-使用实例" class="headerlink" title="5.2 使用实例"></a><font size=3>5.2 使用实例</font></h3><details class="folding-tag" blue><summary> 点击查看实例 </summary>
              <div class='content'>
              <figure class="highlight c"><figcaption><span>test.c</span></figcaption><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;stdio.h&gt;</span></span></span><br><span class="line"><span class="meta">#<span class="keyword">include</span> <span class="string">&lt;unistd.h&gt;</span></span></span><br><span class="line"></span><br><span class="line"><span class="type">int</span> <span class="title function_">main</span><span class="params">(<span class="type">int</span> arc, <span class="type">char</span> *argv[])</span></span><br><span class="line">&#123;</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;每个用户的最大并发进程数: %ld\n&quot;</span>, sysconf(_SC_CHILD_MAX));</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;主机名最大长度: %ld\n&quot;</span>, sysconf(_SC_HOST_NAME_MAX));</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;系统节拍率: %ld\n&quot;</span>, sysconf(_SC_CLK_TCK));</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;系统页大小: %ld\n&quot;</span>, sysconf(_SC_PAGESIZE));</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;一个进程可以打开的最大文件数: %ld\n&quot;</span>, sysconf(_SC_OPEN_MAX));</span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure><p>在终端执行以下命令编译程序：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">gcc test.c -Wall # 生成可执行文件 a.out </span><br><span class="line">./a.out # 执行可执行程序</span><br></pre></td></tr></table></figure><p>然后，终端会有以下信息显示：</p><figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">每个用户的最大并发进程数: 15308</span><br><span class="line">主机名最大长度: 64</span><br><span class="line">系统节拍率: 100</span><br><span class="line">系统页大小: 4096</span><br><span class="line">一个进程可以打开的最大文件数: 1024</span><br></pre></td></tr></table></figure>
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